Companies that used to focus on technology and electronics such as Tesla have expanded recently into the automotive industry to a point that it begins to make more sense to create certain pieces of the car in-house. The latest: the Model X’s second-row seats.

In August, Chief Executive Officer Elon Musk told investors it was difficult to make the seats, which he described as a “sculptural work of art, but a very tricky thing to get right.” They were so challenging that they led him to reduce the electric-car maker’s delivery forecast that month to as few as 50,000 from 55,000, which set off a wave of skepticism over his ambitious plans.

“We have substantially in-sourced the seats at this point,” Musk said Tuesday during the third-quarter earnings call with analysts. “Tesla is producing its own seats.”

Musk has long been a fan of doing things on his own as much as possible, such as building the world’s largest battery factory outside of Reno, Nevada, to streamline production and reduce costs to bring a more-affordable car — the Model 3 — to market. When an analyst asked Musk about the enormous costs of the automotive industry, Musk said that Tesla is becoming more capital-efficient.